IMPROVEMENT OF THE POTATO. 4l^ 



keep potato varieties lastingly high in yield." It is exceedingly in- 

 teresting to note, however, that Westermaeier (106) who suc- 

 ceeded Heine in his work has finally come to the conclusions that 

 in Heine's results the contributing factors were not differentiated 

 from the real question, and that it seems to him that it is question- 

 able whether there is any such thing as variety senility. 



The later conformers to Heine's views are Paulsen (43), Cim- 

 bal and Marek. 



The first weighty objection to this theory was made by Julius 

 Kiihn (64) in 1871. He says: "The theory of a degeneration of 

 the potato is disproved as untenable" and continued for several 

 years thereafter to combat Aitken's theory. Busch (15) continued 

 the opposition and seems to be really the first to recognize the true 

 question. He says : "A degeneration in the sense of an increasing 

 deterioration through the weakness of old age,, does not exist." 

 His views were endorsed and enlarged upon by Wollny (108), 

 Liebscher (66), Girard (45), Thiele (96) and Fischer (33) who 

 have all considered the question apart from that of degeneration 

 through lack of adaptation to environment. 



Ehrenberg (29) in 1904 makes a complete survey of data of 

 Heine, of the deutschen Kartoffelkultursta'tion, and of Paulsen, the 

 first and last of these running from 1877 to 1903. He discusses all 

 the contributing sources of error and comes to the conclusion that 

 "Kin Altern der Kartoffel gibt as aller Wahrscheinlichkeit nicht." 

 And indeed, it appears that the people who have considered this 

 single question are unanimous in opposition to the hypothesis of 

 variety senility. The English and American writers do not seem 

 to have considered the questions apart, although Bailey (5 p. 380) 

 and probably others have recognized the division. He says : 



"The presumption is that varieties propagated by buds wear out sooner 

 than those propagated by seeds, for the experiments of Darwin and others have 

 shown that the special office of seed propagation is to increase the virility of the 

 species through cross fertilization. It must follow therefore, that in the ab- 

 sence of cross fertilization virility must be less. 



"But we do not need to consider this phase of the question, for we are 

 concerned with variation (that is, running out) rather than with ultimate 

 longevity (or wearing out). Further, it is also probable that any tendency 

 toward weakness through lack of fertilization is fully counterbalanced by the 

 protection which such varieties receive under cultivation." 



The work of the U. S. Agricultural Experiment Stations bear- 

 ing the nearest relation to this question are those experiments deal- 

 ing with cormparative value of home grown and northern seed 

 tubers. There is a wide spread belief both in this country and in 



